net: phy: mscc: fix firmware paths

The firmware paths for the VSC8584 PHYs not not contain the leading
'microchip/' directory, as used in linux-firmware, resulting in an
error when probing the driver. This patch fixes it.

Fixes: a5afc167 ("net: phy: mscc: add support for VSC8584 PHY")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>